Friday Deep-Sea Picture: Elevators to the Deep

Sometimes the sub just can’t carry enough or you want to get more work done than you really have time to. Thats why some brilliant deep-sea scientist invented the elevator!

The yellow balls at the top are for floatation, which keeps the elevator neutrally bouyant. You can put all sorts of things on the basket of the elevator, including thermal insulated boxes for keeping animals cold on the ride up.

How does the elevator work? Well, we put weights on the bottom and hoist it overboard with a transponder. It sinks, hopefully close to where we want it to end up. When we arrive in the sub to do our work, we use the signal from the transponder to navigate our way to the elevator. Once we find it, we pick it up in the mechanical arm of the sub and move it to where we want it. When we have it loaded up (or unloaded if we need to bring down heavy equiptment), we snip off the weights and watch it float back up to the surface. Once it reaches surface the ship’s crew up on the deck usually spot it first and reel it in. Clever huh!

We did that ‘on the cheap’ this past summer. We wanted to put out some hydrophones to listen for acoustic tags, but in an area INFESTED with recreational boaters, we didn’t want surface floats. So, I suggested to the undergraduate doing the research that we use some light duty line tied to an expendable weight (In our case a mesh bag of rocks), and then use enough line to bring hydrophone, supported by trawl floats, 20 meters below the surface.
Once deployed, and when ready for retrieval, we would use the boat’s depth sounder to position us directly over the subsurface floats, then deploy the ROV to that depth, and sweep-search for the line/floats using the scanning sonar. Once acquired, we would home in on the sonar target, acquire the line visually, then snip it with the ROV’s cutting claw nearer to the bottom. Worked like a charm! I’d rather have had the expensive moorings, but science sometimes has to get done on a budget, right?
If anyone’s interested, there’s a clip of the mooring/retrieval in the little promo video they had me make for the school:http://rem.sfu.ca/fishgrp/ROVvideoCJWalters-Small.wmv